[Feature Request] Add fullscreen / expand button to embedded content

Is your feature request related to a problem? Embedded content in Outline is currently displayed within a constrained area of the document. For complex embedded content such as architecture diagrams, dashboards, interactive applications, or documentation, the available space is often insufficient for comfortable viewing and interaction. Although some embedded providers support fullscreen natively, there is no consistent way to expand any embed directly within Outline. Describe the solution you'd like Add a Fullscreen / Expand button to embedded content, allowing users to view and interact with it using the entire screen without leaving the current Outline document. Ideally: • Display an expand/fullscreen icon when hovering over an embed. • Allow the embed to occupy the full browser viewport. • Support interactive embedded content, not just videos. • Allow exiting fullscreen using Esc or a close button. • Restore the original …